Molecular mechanism of 1,25-dihydroxyvitamin D3inhibition of adipogenesis in 3T3-L1 cells
Tóm tắt
We have investigated the molecular mechanism whereby 1,25-dihydroxyvitamin D3[1,25(OH)2D3] inhibits adipogenesis in vitro. 1,25(OH)2D3blocks 3T3-L1 cell differentiation into adipocytes in a dose-dependent manner; however, the inhibition is ineffective 24–48 h after the differentiation is initiated, suggesting that 1,25(OH)2D3inhibits only the early events of the adipogenic program. Treatment of 3T3-L1 cells with 1,25(OH)2D3does not block the mitotic clonal expansion or C/EBPβ induction; rather, 1,25(OH)2D3blocks the expression of C/EBPα, peroxisome proliferator-activated receptor-γ (PPARγ), sterol regulatory element-binding protein-1, and other downstream adipocyte markers. The inhibition by 1,25(OH)2D3is reversible, since removal of 1,25(OH)2D3from the medium restores the adipogenic process with only a temporal delay. Interestingly, although the vitamin D receptor (VDR) protein is barely detectable in 3T3-L1 preadipocytes, its levels are dramatically increased during the early phase of adipogenesis, peaking at 4–8 h and subsiding afterward throughout the rest of the differentiation program; 1,25(OH)2D3treatment appears to stabilize the VDR protein levels. Consistently, adenovirus-mediated overexpression of human (h) VDR in 3T3-L1 cells completely blocks the adipogenic program, confirming that VDR is inhibitory. Inhibition of adipocyte differentiation by 1,25(OH)2D3is ameliorated by troglitazone, a specific PPARγ antagonist; conversely, hVDR partially suppresses the transacting activity of PPARγ but not of C/EBPβ or C/EBPα. Moreover, 1,25(OH)2D3markedly suppresses C/EBPα and PPARγ mRNA levels in mouse epididymal fat tissue culture. Taken together, these data indicate that the blockade of 3T3-L1 cell differentiation by 1,25(OH)2D3occurs at the postclonal expansion stages and involves direct suppression of C/EBPα and PPARγ upregulation, antagonization of PPARγ activity, and stabilization of the inhibitory VDR protein.
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Arbour NC, Prahl JM, and DeLuca HF.Stabilization of the vitamin D receptor in rat osteosarcoma cells through the action of 1,25-dihydroxyvitamin D3.Mol Endocrinol7: 1307–1312, 1993.
Hida Y, Kawada T, Kayahashi S, Ishihara T, and Fushiki T.Counteraction of retinoic acid and 1,25-dihydroxyvitamin D3 on up-regulation of adipocyte differentiation with PPARgamma ligand, an antidiabetic thiazolidinedione, in 3T3–L1 cells.Life Sci62: PL205–PL211, 1998.
Jurutka PW, Hsieh JC, MacDonald PN, Terpening CM, Haussler CA, Haussler MR, and Whitfield GK.Phosphorylation of serine 208 in the human vitamin D receptor. The predominant amino acid phosphorylated by casein kinase II, in vitro, and identification as a significant phosphorylation site in intact cells.J Biol Chem268: 6791–6799, 1993.
Kawada T, Kamei Y, and Sugimoto E.The possibility of active form of vitamins A and D as suppressors on adipocyte development via ligand-dependent transcriptional regulators.Int J Obes Relat Metab Disord20,Suppl3: S52–S57, 1996.
Querfeld U, Hoffmann MM, Klaus G, Eifinger F, Ackerschott M, Michalk D, and Kern PA.Antagonistic effects of vitamin D and parathyroid hormone on lipoprotein lipase in cultured adipocytes.J Am Soc Nephrol10: 2158–2164, 1999.
Shi H, Norman AW, Okamura WH, Sen A, and Zemel MB.1a,25-dihydroxyvitamin D3 inhibits uncoupling protein 2 expression in human adipocytes.FASEB J16: 1808–1810, 2002.
Student AK, Hsu RY, and Lane MD.Induction of fatty acid synthetase synthesis in differentiating 3T3-L1 preadipocytes.J Biol Chem255: 4745–4750, 1980.